The National Transportation Safety Board said that nighttime flying in poor weather conditions likely contributed to the three crashes in question, according to CNN.

Officials have grown concerned over the frequency of helicopter crashes in the past several months. In fact, nine medical helicopter crashes during 2007 and 2008 have killed 35 people, and the NTSB has released information related to all of them.

In the case of a crash in Maryland, the NTSB found that air traffic controllers were "casual and sloppy" in guiding a state police medevac helicopter, according to the Baltimore Sun. The pilot may also have used outdated weather information, but the NTSB said there was no clear cause of this crash.

In February 2009, the NTSB will hold hearings on the frequency of medical helicopter crashes. The board recommended safety improvements to the FAA in 2006, but the suggestions were not entirely followed.

In a written statement, Robert Sumwalt, chairman of the hearing's board of inquiry, stated, "This hearing will be extremely important because it can provide an opportunity to learn more about the industry so that possibly we can make further recommendations that can prevent these accidents and save lives."

Dr. Marc R. Matthews of Phoenix and Dr. Jeffrey P. Salomone of Atlanta, for example, said that emergency medical transports could have been used instead of the helicopters in a number of instances.

“I’m all for heroes—for the firefighters who climbed up the stairs while the World Trade Center was falling down or anyone else who risks their life to help people,” Salomone said. “But it’s a real tragedy to think someone could die trying to help a patient who didn’t have a life-threatening injury to begin with.”

In its review of documents associated with the 26 deadly medevac crashes in the United States since 2003, the Baltimore Sun claimed that the helicopters were sometimes used in situations that were not immediate or life-threatening. “At least eight involved patients who waited longer for a helicopter than a ground ambulance might have needed to drive them to a hospital. And at least six were for patients discharged soon after a helicopter dropped them off at a hospital, or who survived a lengthy ambulance ride after the helicopter sent to get them went down,” according to the Sun.

Maryland’s program has been under close watch. In September a whistleblower warned federal authorities that mismanagement in the program could lead to adverse consequences. Another individual said the helicopter in the Sept. 28 accident had been damaged in an incident years earlier, according to The Examiner.

In 2005, USA Today reported that “a deadly trend of pilot errors, industry carelessness and poor government oversight has driven the number of air ambulance crashes to record levels.” A 2006 report indicated that 29 of 55 air ambulance crashes between January 2002 and January 2005 could have been prevented.

The NTSB has noted some recurring themes in medical helicopter crashes, including inconsistent dispatch procedures and limited requirements to use “safety-enhancement technologies” like night vision goggles, according to CNN. The NTSB can make safety recommendations for the medical flight industry, but only the FAA can make them mandatory.

On Aug. 31, 2008, an Air Evac medical transport helicopter crashed in Indiana, instantly killing the three crew members on board. This was the fifth accident involving an Air Evac helicopter in recent years.

The crew wasn’t on an ambulance run, but was traveling to a tractor pull event. It’s common practice, Air Evac told the Indianapolis Star, for its workers to attend community events.